1. Field of the Invention
The present invention generally relates to a fault diagnosis device that executes a fault diagnosis of at least three sensors each configured to detect a temperature of a different measurement entity.
2. Background Information
A known technology for executing a fault diagnosis of a temperature sensor uses detection values of several reference temperature sensors that are different from the temperature sensor being subjected to fault diagnosis.
Japanese Laid-Open Patent Application No. 2004-339969, for example, discloses a technology that includes a radiator, a cooling water passage that circulates cooling water of an internal combustion engine to the radiator, a thermostat that opens and closes the cooling water passage according to a cooling water temperature inside the cooling water passage, a radiator-side cooling water temperature that detects a cooling water temperature at a point located toward a radiator from the thermostat, an engine-side cooling water temperature that detects a cooling water temperature at a point located toward an engine from the thermostat, and an intake air temperature that detects an intake air temperature. If the temperature detected by the radiator-side cooling water temperature sensor is greatly different from the temperature detected by the engine-side cooling water temperature sensor and the temperature detected by the intake air temperature sensor after the engine has been stopped for a predetermined amount of time corresponding to when the temperatures near each of the sensors should be substantially equal to an outside ambient temperature, then the radiator-side cooling water temperature sensor is determined to have faulted regardless of whether the temperature detected by the engine-side cooling water temperature sensor and the temperature detected by the intake air temperature sensor are close together.
However, with the technology of Japanese Laid-Open Patent Application No. 2004-339969, since the timing at which the temperature sensor fault diagnosis is executed occurs after the engine has been stopped for a predetermined amount of time corresponding to when the temperatures near each of the radiator-side cooling water temperature sensor, the engine-side cooling water temperature sensor, and the intake air temperature sensor should be substantially equal to the outside ambient temperature, it is not possible to execute a fault diagnosis of the temperature sensors when the engine is started before the predetermined amount of time has elapsed and the fault diagnosis of the temperature sensors will tend to be delayed.